Method of depositing an oxymethylene polymer from formaldehyde in the vapor form on cellulosic textiles and the resulting product

ABSTRACT

Highly purified anhydrous monomeric formaldehyde vapor was prepared for immediate deposition on the surface of fibers of cotton. The process produced fabrics with enhanced physical properties with the deposition of oxymethylene polymer with molecular weights up to 18,000 and without significant crosslinking of the cellulosic chains. Supplementary treatments were applied to the oxymethylene polymer treated fabrics to further enhance the textiles with various desirable &#39;&#39;&#39;&#39;washwear&#39;&#39;&#39;&#39; characteristics.

United States Patent Brenner et a1.

[ 51 May 16, 1972 METHOD OF DEPOSITING AN OXYMETHYLEN E POLYMER FROMFORMALDEHYDE IN THE VAPOR FORM ON CELLULOSIC TEXTILES AND THE RESULTINGPRODUCT Inventors: Walter Brenner, Teaneck, NJ.; Jagadish ChandaGoswami, New York; Barry A. Rugs, Bronx, both of NY.

Assignee: The United States of America as represented by the Secretaryof Agriculture Filed: May 12, 1970 Appl. No.: 23,163

US. Cl ..8/1 16.4, 8/116.2, 8/120, 8/129, S/DIG. ll, 8/1163, 252/438,8/1492,

Int. Cl. 13/14, D06m 13/54, 006m 13/42 Field 01 Search ..8/116.4, 116.2,120, 116.3, 8/129 [56] References Cited UNITED STATES PATENTS 3,545,91312/1970 .loarder et a1 ..8ll 16.4

OTHER PUBLICATIONS .loarder et aL, Textile Research Journal, 39, 49- 54I969 Primary Examiner-George F. Lesmes Assistant Examiner-.1. CannonAttorney-R. Hoffman and W. Bier [57] ABSTRACT 4 Claims, 5 DrawingFigures PATENTEUMY 16 I972 SHEET 1 OF 5 FIGJ I N VENTORS WALTER BREN NERJAGADISH CHANDRA soswm BARRY A. RUGG ZZ ATTRNEY PATENTEUMAY 16 19723,663,158 snznanrs 8 8 3 8 0 (9s) aouvumswau INVENTORS WALTER BRENNERJAGADISH CHANDRA I BARRY ARUGG GOSNAM ATTORNEY PATENTEDMAY 16 m2 SHEET 3UF 5 INVENTORS WALTER BRENNER JAGADISH cHAmm 609mm BARRY ARUGG M91$205.2 IGzwd V m. S Q m o. m m h m m o Q 0 (90) HQNVLLIWSNVHL HOO- OOOmOOQW ATJTORNEY PERCENT GROSS WT. GAIN PATENTEDMAHBIQYB Wing-1,158

SHEEI [1F 5 o l 1 1 I 1 I o 5 IO I5 vAPoR EXPOSURE TIME (MIN) F I G. 4

INVENTORS WALTER BRENNER JAGADISH CHAMJQA GOSWAMI BARRY ARUGG ATTORNEY VPATENTEDMM 16 m2 SHEEI 5 OF 5 INVENTOJE WALTER BRENNER ATTORNEY METHODOF DEPOSITING AN OXYMETHYLENE POLYMER FROM FORMALDEHYDE IN THE VAPORFORM ON CELLULOSIC TEXTILES AND THE RESULTING PRODUCT A non-exclusive,irrevocable, royalty-free license in the invention herein described,throughout the world for all purposes of the United States Government,with the power to grant sublicenses for such purposes, is hereby grantedto the Government of the United States of America.

This invention relates to a novel process for the formation anddeposition of oxymcthylene polymers from formaldehyde monomer in thevapor form on cellulosic textiles and to the composite polymericproducts resulting from said process.

A very substantial effort has been made in the past and is continuingtowards developing cellulosic textiles with a superior balance ofperformance properties, particularly so as regards the realization ofdurable wrinkle resistance or socalled wash-wear" characteristics whileretaining tensile and tear strength, abrasion resistance, the uniquecomfort factor and other desirable qualities of cellulosic textiles, inorder to better meet specific consumer requirements. The treatment ofcellulosic textile materials with formaldehyde or formaldehyde donorshas long been experimented with for obtaining a more desirable balanceof cellulosic textile properties. Given suitable reaction conditions,formaldehyde treatments result in crosslinking of cellulosic chains andthe development of marked wrinkle resistant properties but otherimportant physical characteristics including tensile strength, tearstrength, elongation, and abrasion resistance are adversely affected.Typically, tensile strength losses amount to as much as 50-60 percent orgreater. The loss in certain important physical properties associatedwith the strength and durability of the many formaldehyde-treatedcellulosic textiles may be related to the nature of the generallystrongly acidic catalysts and/or substantially elevated treatmenttemperatures-reaction conditions which attack the cellulose as well asto the short crosslinks formed.

Accordingly, it is an object of the present invention to treatcellulosic materials with formaldehyde in such a manner that certaindesirable physical properties such as tensile strength, elongation, tearstrength, abrasion resistance, hand and appearance are significantlyimproved.

Another object is to treat cellulosic fabrics with formaldehyde so as toproduce uniform and even oxymethylene polymer deposits onto thecellulose fiber surfaces without significantly altering such desirablephysical properties as tensile strength, elongation, tear strength,abrasion resistance, hand and appearance.

A further object is to treat cellulosic fabrics with formaldehyde so asto produce uniform and essentially continuous oxymethylene polymerdeposits on cellulose fibers without effecting any significant amount ofcrosslinking of the cellulosic chains.

An additional object is to treat the oxymethylene polymercoatedcellulosic textiles in such a manner that wash and wear characteristicscan be achieved without the large decreases in important physicalstrength and durability characteristics generally associated withformaldehyde-treated cellulosic textiles.

Yet another object is to obtain modified oxymethylene polymer-coatedcellulosic textiles with a superior balance of "wash-wear"characteristics and physical strength, durability properties andappearance than hitherto attainable.

A still further object is to obtain such modified oxymethylenepolymer-coated cellulosic textiles with a superior balance of "wash-wearcharacteristics and physical strength, durability properties andappearance using only low cost and therefore economically attractivetreating agents and procedures.

Yet another further object is to obtain such modified oxymethylenepolymer coated cellulosic textiles with a superior balance of wash-wear"characteristics and physical strength, durability properties andappearance with treating agents and techniques amenable to continuousprocessing.

Still another additional object is to obtain such modified oxymethylenepolymer coated cellulosic textiles with a superior balance of wash-wear"characteristics and physical strength, durability properties andappearance which are permanently stabilized.

Still further objects and the entire scope of applicability of thepresent invention will become apparent from the following detaileddescriptions; it should be understood, however, that the detaileddescriptions and physical examples while indicating preferred embodimentof this invention are given by way of illustration only since manypossible changes and modifications within the scope of this inventionwill become apparent to those skilled in the art from these detaileddescriptions.

it has now been found that these objects can be obtained by utilizingthe specific procedures to be discussed hereafter. Basically, theseprocedures include two reactions. The first one is the reaction offormaldehyde with cellulose under conditions which result in theformation of uniform and essentially continuous oxymethylene polymerdeposits on cellulose fibers widrout significant crosslinking of theceliulose chains. This is accomplished by treating cellulosic fabricswith strictly anhydrous monomeric formaldehyde vapor under basiccatalytic conditions. The oxymethylene polymer deposits formed mayoptionally be stabilized against thermal unzippering" by end capping theoxymethylene hydroxyl end groups with acetic anhydride or other suitablereagents. The second step involves the treatment of the oxymethylenepolymer-coated cellulosic fibers with one of the large and still growingnumber of cellulose crosslinking agents and particularly that groupwhich have become known as the methylol amides. Quite conventionalcrosslinking textile finishing technology can be employed for thisprocessing ste During the second step there is developed a substantialincrease in both wet and dry wrinkle recovery with only relativelyminimal effects on other important cellulose fabric properties includingtensile and tear strengths, elongation, abrasion resistance andappearance. The resulting better overall balance of the treatedcellulose fabrics performance properties is attributed to the presenceof the uniform and essentially continuous tough oxymethylene polymerdeposits on the cellulosic fibers obtained in the first processing step.By obvious appropriate modifications of this invention, cellulosicfabrics can be pleated or creased after the fabrics have been convertedinto apparel, etc.

The advantageous balance of properties imparted by the processes of thepresent invention including greatly improved wet and dry wrinklerecovery values and a high degree of retention of the desirable tensilestrength, tear strength, elongation, abrasion resistance and appearanceare all permanently embedded in the fabric. Thus, these properties haveproven stable for in excess of 10 washings.

As previously described the present invention enables the deposition ofuniform and essentially continuous coatings of oxymethylene polymer fromgaseous monomeric formaldehyde and the subsequent crosslinking of thepolymer-coated cellulose fibers with any of the many available cellulosecrosslinking agents with particular emphasis but not in any way limitingon the industrially used methylol amides. The present inventioneffectively overcomes the most deleterious effects of the conventionalcellulose crosslinking agents on cellulose textile by applying them tosuch oxymethylene polymer coated cellulose composite. While the mode ofaction of this invention is not entirely clear and we do not wish to bebound by any one explanation of the observed experimental fact, it issuggested that the presence of the physically tough and continuousoxymethylene polymer coatings on the cellulose fibers in some waymitigates the well known undesirable effects of these cellulosecrosslinking agents.

As the cellulosic fabric there can be employed cotton, linen, hemp,ramie, sisal, rayons, and cellulose esters and/or ethers as well asmixtures of these fabrics with each other and/or synthetic fabricsincluding polyamides, polyesters, and acrylics. The invention isconsidered to be particularly applicable to the treatment of cottonfabric material such as cotton cloth.

in accordance with the above discussions, therefore, this inventioncomprises a formaldehyde monomer based vapor phase polymerizationprocess more specifically comprising the exposure of suitably catalyzedcellulosic cloths to purified anhydrous formaldehyde vapor which thenpolymerizes to high molecular weight polyoxymethylene even at ambienttemperatures selectively onto the catalyzed cellulosic surfaces toproduce a uniform and essentially continuous oxymethylene polymericcoating thereon. Also, as noted earlier as a second processing step, itinvolves the treatment of such polyoxymethylene coated cellulosicsurfaces with one of the many available cellulose crosslinking agentsand with a controlled amount of crosslinking exhibiting a superiorbalance of performance properties including substantially higher dry andwet wrinkle recovery values without incurring the so undesirable markedlosses in tensile strength, tear strength, elongation, abrasionresistance, etc. characteristic of conventionally treated crosslinkedcellulosic fabrics.

Initially, high molecular weight polyoxymethylene polymer deposits areobtained by the immersion of cellulosic fabrics into a suitable alkalinecatalyst solution at ambient temperatures and in air and then exposingthe catalyzed cloths to purifled anhydrous monomeric fonnaldehyde vapor.The time lag between the catalyst immersion process and the exposure ofthe catalyzed cellulosic cloth to the purified anhydrous monomericformaldehyde vapor is not critical and conveniently may amount tobetween 5 and minutes for many experiments. A typical catalyst systemconsists of a tertiary amine in the presence of a suitable amount of ananti-oxidant dissolved in a halogenated solvent. A preferred embodimentof such a catalyst system comprises a solution of tributylamine anddiphenylamine antioxidant dissolved in carbon tetrachloride. Thepurified monomeric anhydrous formaldehyde vapor can be obtained in anynumber of well known ways, one preferred method being its generationfrom heating a paraformaldehyde-parafiin slurry at l l5-120 C. Thisformaldehyde gas generation is preferably conducted under inertconditions such as dry nitrogen gas. Purified anhydrous formaldehydevapor is then carried in dry nitrogen gas to a polymerization chambercontaining the catalyzed cellulosic cloths. Constructional features ofthe polymerization chamber and associated physical equipment set up willbe described below and are shown in FIG. I of the accompanying drawing.

Oxymethylene polymer coatings are then deposited onto the surfaces ofthe cellulosic fibers in amounts depending upon such reaction variablesas formaldehyde vapor concentration, reaction time, temperature, etc.Polymer deposits ranging from as little as 2 percent or less to inexcess of 50 percent based on the weight of the cellulosic fabric arereadily and reproducibly obtained by appropriate variations of the abovereferred to significant reaction variables. Typically, 10 percentpolymer add-ons can be obtained in approximately 10 minutes exposuretime to the formaldehyde vapor with one rather convenient set ofreaction conditions. No cellulose crosslinking occurs as evidenced bysolubility of the cellulosic substrate in solvents, such ascupriethylenediamine.

As is well known, the thermal stability of oxymethylene polymers issubstantially enhanced by end capping their residual hydroxyl end groupsto retard high temperature depolymerization or unzippering," a reactionwhich can lead to the evolution of formaldehyde gas. One convenient andwidely used procedure involves the esterification reaction of theoxymethylene polymer hydroxyl end groups with acetic anhydride. Otherend-capping treatments include etheriflcation with alcohols, reactionswith chloroalkylethers and reactions with epoxides or isocyanates. Ifdesired, this can be accomplished with the oxymethylene polymer-coatedcellulosic fabrics by heating them in acetic anhydride solutions. Atypical set of reaction conditions for such end-capping treatmentsinvolves heating the polymer-coated cellulosic fabrics in aceticanhydride solutions for approximately 30 minutes at I40 C. in thepresence of a small amount of an esterification catalyst in order tospeed up the esterification reaction. This treatment reduces thesolubility of the cellulosic substrates in solvents such ascupriethylenediamine.

The uncapped polyoxymethylene coatings can be removed from thecellulosic fibers by solvent extraction in hot dimethylformamidefollowed by precipitation at ambient temperatures, purification bywashing and, finally, vacuum drying. The chemical composition can beconfirmed quite readily by means of infrared analysis. Melting pointdeterminations and other physical property measurements can also becarried out for identification purposes. Experiments can also be carriedout involving the dissolution of the cellulose in cupriethylenediaminesolvent leaving behind shells of polyoxymethylene polymer. Thesestudies, which confirm the absence of any chemical reaction between theoxymethylene polymer deposits and the cellulosic textiles and alsodemonstrate that no cellulose crosslinking has occurred, are furtherclarified by FIGS. 2 and 3 of the accompanying drawing. FIGS. 2 and 3,for example, compare the infrared spectra of a commercial oxymethylenepolymer film with an extracted ox ymethylene polymer deposit from acoated cotton type cellulosic textile. The longitudinal photomicroscopicview of the oxymethylene polymer shows shells remaining after immersionof oxymethylene polymer-coated cotton cloths with various amounts ofpolymer coating add-on's in cupriethylenediamine solvent. Similarstudies have also been carried out with so-called end-cappedoxymethylene polymercoated cellulosic textiles. The results of thesolvent extractions are similar to the ones described immediately above,except that the cellulose substrate solubility in cupriethylenediamineis significantly reduced. Typical oxymethylene polymer extractionproducers involve a 2-hour refluxing period in dimethylformamide. Theend-capped polymer is extracted by refluxing for 6 hours indimethylformamide.

Photomicrographic studies have also been made in order to ascertain thelocation of these oxymethylene polymer deposits on the cellulosictextiles. Differential staining of the cross section of fiber specimensshows that the polymer deposits are located along the outer periphery ofthe fibers. A blue dispersion dye, Setacyl Blue 2 GS conc. 250 percent,was employed to stain the oxymethylene polymer-coated cotton clothsamples and photomicrographic cross sections were studied.

The following examples illustrate processes for the deposition of suchoxymethylene polymer deposits from formaldehyde monomer in the vaporphase on cellulosic textiles.

EXAMPLE 1 Cotton print cloths X 80 desized, bleached, and mercerizedwere obtained and cut into lO-inch X 6-inch fabric samples for use inthe vapor phase polymerization studies, which are described below.Suitably conditioned cloth samples were catalyzed by immersing in acatalyst solution comprising 7.5 cc. of tributylamine and 3.6 grams ofdiphenylamine dissolved in 1,500 cc. of carbon tetrachloride for lminute. The catalyzed conditioned cotton cloth samples were then exposedto purified anhydrous formaldehyde vapor in a specially constructedvapor phase polymerization chamber for predetermined time periods. Theformaldehyde vapor was generated by heating a slurry of paraformaldehydein paraffin oil prepared by mixing thoroughly 75 grams ofparaformaldehyde with 300 ml. of paraffin oil in a half liter resinkettle.

A general schematic diagram of the apparatus employed, from which wasderived the bulk of the experimental data of this invention and whichdemonstrates the manner in which the vapor phase coating of cotton clothsamples with polyoxymethylene is carried out most successfully, isdepicted in FIG. 1 of the accompanying drawing.

Referring with more particularity to FIG. 1, the flow of gases isgenerally from left to right. The nitrogen cylinder 11 provides theinert propellant gas upon opening valve 12. The nitrogen gas passesthrough drying tube 13 and the rate of flow is measured by rotometer 14.The dried gas then passes via tube 15 through three-way valve 16 whichwas installed so as to provide pressure readings through the use ofmercury manometer l7, and then passes through sintered glass disc 19into half-liter Pyrex resin kettle 21 which contains theparaformaldehyde and oil slurry 20. The kettle is covered tightly andheated by heating mantle 22. The thermometer 18 provides measurement ofthe temperature of the slurry.

The oxymethylene produced in the kettle is let out throughwater-jacketed condenser 23 when stopcock 24 is in the open position andthence passes through tube 26 into first trap 29 via inner tube 28 whichconnects to the trap through flexible tube 27. First trap 29 is immersedin a first Dewar flask 30 which contains coolant 31 consisting ofammonium chloride and ice.

Second trap 34 is immersed in a second Dewar flask 32, being cooled by asecond coolant 33, identical to coolant 31, and receives theoxymethylene through tube 35 into the trap and out through tube 37 viaflexible connector 36.

The three-way stopcock 38 controls the flow of argon, provided by argoncylinder 42, through tube 40 when valve 41 is opened. The manipulationof three-way stopcock 38 serves to provide the inert gas which evacuatesthe vapor phase polymerization chamber 45 as the gases would flowthrough straight external tube 43 which leads to the chamber throughinner dispenser tube 44 when stopcock 38 is turned so as not to letgases out through outlet 39 which leads to an absorber hood (not shown).

The vapor phase polymerization chamber 45 is designed to hold clothsamples 47 suspended by sample holders 46, and the exhausted gases arelet out to absorber hood (not shown) through outlet 48 after thereaction is complete.

The vapor phase polymerization chamber 45 employed in this experimentconsisted of an 8-inch 8-inch X 12-inch stainless steel-lined vacuumoven. The cloth samples 47 were mounted on stainless steel frames, whichwere then suspended inside the polymerization chamber from a sampleholder 46, also constructed from stainless steel. A second chamberconsisted of a half liter Pyrex resin kettle 21. which was jacketed withan electric heating mantle 22. This kettle contained the paraffinoil-paraformaldehyde slurry from which the formaldehyde monomer vaporwas generated by heating to l l$-l20 C. The monomer was carried to thepolymerization unit in dry nitrogen gas from nitrogen cylinder 11.

Water, methanol, and formic acidthe usual byproducts from the pyrolysisof paraformaldehyde-are known to cause considerable polymerization ofmonomeric formaldehyde leading to water soluble low molecular weightproducts. The nitrogen-formaldehyde gas stream was, therefore, purifiedby successive passage through two traps, namely, traps 29 and 34, cooledto 1 5 to l 7 C. by respective coolants 31 and 33 consisting of ammoniumchloride and ice, in order to condense such undesirable byproducts.

The polymerization chamber 45 containing the catalyzed cotton clothsamples 47 was flushed with argon gas from argon cylinder 42 in order todisplace air before admitting the purified formaldehyde-nitrogen gasstream. This gas mixture was then directed into the chamber, thuscausing polymerization of the formaldehyde vapor on to the surfaces ofthe catalyst activated cotton cloth samples. Excess reagent gas mixtureleft the polymerization chamber 45 through outlet 48 and was condensedin a cold trap.

Typical specific reaction conditions included a nitrogen gas flow rate,as measured by rotometer 14, in the order of 0.8 to 1.2 liters/min., aparaformaldehyde-paraffin oil slurry temperature of l l5-l 20 C. asmeasured by thermometer 18 and a polymerization chamber temperature ofC. The exposure time of the catalyst activated cloth samples to thepurified monomer formaldehyde vapor was varied in order to obtaindifferent polymer add-on's and to ascertain such efi'ects on thepertinent physical and chemical properties of the cotton samples.Experimental results relating the exposure time of the catalyst cottoncloth samples to the oxymethylene polymer add-on's are shown in FIG. 4of the accompanying drawing.

The oxymethylene polymer coating was recovered from the cotton cellulosesubstrate by extraction in refluxing dimethylformamide for 2 hoursfollowed by precipitation at ambient temperatures, filtering, washingwith acetone and ether and vacuum drying at 50 C. Thin films of polymerwere prepared by pressing an appropriate amount of the dried recoveredpolymer at 30 C. in a laboratory press. identification was accomplishedby comparing an infrared spectrograph of this material with that of acommercially produced polyoxymethylene film. Melting point was 165 C.The data obtained were analogous to the information presented in FIGS. 2and 3 of the accompanying drawing, except for the absence of C 0 groupsintroduced in the commercial product by end capping via esterificationwith acetic anhydride. The relative viscosity of the recoveredpolyoxymethylene was determined in a viscometer utilizing a 0.5 percentsolution of oxymethylene polymer at 60 C. in p-chlorophenol containing 2percent by weight of alpha pinene. The inherent viscosity was calculatedfrom the equation: inherent viscosity in relative viscosity/C whererelative viscosity solution viscosity/solvent viscosity, C concentrationof solute in solution (grams polymer per 100 ml. of solution). It wasfound to be 0.865. The inherent viscosity was then related to themolecular weight using the expression inherent viscosity 3.82Xl0 M, Themolecular weight (M,,) calculated in this manner was approximately 1 1,000-] 2,000.

Pertinent physical properties of oxymethylene polymercoated X 80 cottonprint cloth are summarized in Table l as a function of polymer add-on.The data show not only retention but even some improvement in abrasionresistance and tear strength, etc. As expected, wrinkle recovery valueswere not changed by this polymer deposition process in which neither thevapor phase deposited polyoxymethylene nor the cellulose substrate werecrosslinked. This example demonstrates the retention and even shows someimprovement in selected important physical properties of theoxymethylene coated cotton cloths prepared in accordance with theteachings of this invention.

EXAMPLE 2 Cotton print cloths 80 X 80 desized, bleached and mercerizedwere obtained and cut into l0-inch X 6-inch fabric samples for use informaldehyde vapor phase polymerization studies. The cloth samples wereconditioned and catalytically activated in the same manner as describedin Example I. The catalyzed cotton cloth samples were then exposed toforrnaldehyde vapor again generated by heating a slurry ofparaformaldehyde in paraffin oil to llS-120 C. The experimental setupwas identical with the one shown schematically in F 1G. I and discussedin Example 1 above, except that the formaldehyde vapor bypassed the twolow temperature traps 29 and 34 and was fed directly into thepolymerization chamber 45.

Polymer deposition occurred on the catalyzed cloth samples 47 in thesame manner as before. The polymer deposits were, however, found to bereadily water soluble and could thus be easily removed from the clothsamples. Further studies showed that the polymer deposits, which werefound to be of quite low molecular weight (below 1,000), did notsignificantly affect any of the pertinent physical or otherwiseimportant properties of the cotton cloth samples. This experiment showsthe importance of purifying the formaldehyde monomer by removal of thebyproducts of the paraformaldehyde pyrolysis including water, methanol,and formic acid, in order to produce high molecular weight oxymethylenepolymer.

EXAMPLE 3 Cotton print cloths, 80x80 desized, bleached, and mercerizedwere obtained and again cut into lO-inch x 6-inch fabric samples for usein additional vapor phase polymerization studies. These were conductedwith the same equipment and employing analogous chemical reagent andprocedures as described in Example 1 except that the time of immersionof the cotton print cloth in the catalyst solution was varied. Theresults in terms of polymer add-on per time unit are shown in Table 2.Immersion time of the cotton print cloth into the carbon tetrachloridecatalyst solution is apparently not a primary variable for the polymerdeposition process described in Example 1.

EXAMPLE 4 Cotton print cloths, 80 X 80 desized, bleached, and mercerizedwere obtained and cut into -inch X 6-inch fabric samples for use invapor phase polymerization studies. In order to study the effects ofpolymerization temperature on polymer deposition a series of experimentswere run during which the temperature in the vapor phase polymerizationchamber 45 was varied between l5 and 60 C. All other procedures andmaterials were the same as described in Example l above.

It was found that polymerization temperatures in the order of C.resulting in substantially lower polyoxymethylene deposition ratesamounted to approximately one-half of the data presented in Example I.However, the molecular weight of the polymer deposits was significantlyhigher. Using previously outlined procedures, it was determined to be inthe order of l7,000-l8,000. Pertinent properties of the oxymethylenepolymer-coated cotton cloths were quite similar to the ones obtainedwhen polymerization was effected at approximately C. Experiments carriedout at 60 C. failed to yield any substantial polymer deposit thussuggesting the existence of a ceiling temperature for the vapor phaseformaldehyde polymerization given in the above-detailed experimen' talconditions.

As indicated, the second step of the above-outlined processing sequenceinvolves the treatment of the oxymethylene polymer cellulosic fabricswith one of the many available large and still growing number ofcellulose crosslinking agents and particularly a compound selected fromthat group of chemicals, which have become known as the methylol amides.While oxymethylene polymer-coated cellulosic fabrics obtained from thevapor phase polymerization of anhydrous formaldehyde onto a cellulosicsubstrate have been experimentally shown to exhibit certain desirableimproved physical strength properties, including tensile strengthelongation, tear strength, abrasion resistance, they requiresubstantially enhanced shape holding properties such as wrinkleresistance, wash-wear characteristics and dimensional stability, toenhance their utility in volume apparel applications. It is the purposeof this secondary treatment to develop such properties withpolyoxymethylene coated fabrics.

TABLE 1 TABLEZ Effect of Catalyst Immersion Time on Polymer Add-0n(formaldehyde vapor phase polymerization at 25 C.)

Immersion Time (sec.)

Exposure Time (min.

b Polymer Sample Add-On The number of crosslinking finishing treatmentswhich has been proposed in the technical literature and experimentallyinvestigated to some extent, is very large indeed. The methylolderivatives of urea and melamine, methylol derivatives of cyclic ureas,and methylol carbamates are among the most effective yet economical andtherefore among the most widely used industrial crosslinking finishingagents. Other types of crosslinking agents that have been employed to alimited extent, include the diepoxides, beta-substituted diethylsulfones, acetals and aziridinyl compounds. The choice of a crosslinkingfinishing treatment frequently represents a rather complex compromisebetween performance and cost applied to a specific product line with agiven production processing capability.

[Physical properties of polyoxymethylene coated cotton cloth samples]Breaking strength, lb."

Abrasion Warp Fill (llux) Tearing resist- Bample Percent Percent Percentstrength, g. lance desigwright elonga- Breaking elongu- Breakinguyuh-snation gain tion strength Lion strength Warp Fill [nilum Control5. B 58. 7 17. 4 37. .l 470 784 s? #l-C 8. 5 63. 4 20. l 34. (l 578 8707 4 #Z-C 2. (1 fl. l) 60. ii 20. 8 39. ll 588 llllB Jll #3-0 5. 5 7. 460. 1 an. u 3n. n 51m .102 1111 #4-(1. .I. 3 7. 4 56. ii 20. 3 39. (l552 Hill 126 #5-(1 r 1-4. 7 7. l til. 5 lil. l 38. I) 541) 892 153 #64.24. 0 ti. 3 66. 2 iii. 3 4 l. l 4315 550 l'M Avg. value of ti smnph-s.Avg. value of 5 runs. Avg. vnluu ul -1 runs. 4 Avg. vuhu- M3 runs.

pr 30 min.

Recognizing this situation, a series of experiments have been carriedout in which oxymethylene polymer coated cellulosic fabrics were treatedwith various types of cellulose crosslinking agents and the resultantcomposite characteristics determined in terms of pertinent textileproperties with emphasis on the development of shape-holdingcharacteristics to be ascertained by tests such as dry and wet wrinklerecovery values. Considerable attention was paid to reproducibility ofresults necessitating the testing of many duplicate samples. Specificchemical types of crosslinking agents which were reacted withpolyoxymethylene treated cellulosic fabrics included the following:

a. methylol derivatives of cyclic ureas, methylol derivatives ofmelamine, methylol derivatives of urea, and methylol carbamates; anunbuffered glyoxal based reactant, and a reactant described as anonresinous cyclic uron derivathe;

b. multifunctional carboxylic acids, e.g., maleic acid, l,2,3,4cyclopentanetetracarboxylic acid; trimellitic acid; mellitic acid andl,2,3,4 butanetetracarboxylic acid;

c. epichlorohydrin and difunctional epoxides.

Experimentally the indicated crosslinking finishing treatments werecarried out by padding oxymethylene polymer coated cellulosic fabricswith suitable catalyzed aqueous solutions of these crosslinking agentsfollowed by drying, heating, washing and drying in accordance with thespecific procedures recommended by the manufacturer of the crosslinkingagent employed. Typical crosslinking conditions for a methylolamide typecrosslinking agent, for example, were the treatment of a cellulosiccloth coated with known amounts of polyoxymethylene, with aqueoussolution comprising weight percent of the active crosslinking agent, 1percent catalyst, e.g., Zn(NO ),-6H,0 or equivalent.2 percent softenerMykon SF polyethylene emulsion or equivalent and 0.1 percent Triton X405 alkylphenoxy ethanol or equivalent for approximately 10 minutes atambient temperatures. The samples were then dried for minutes in an aircirculating oven at 80 C. Crosslinking was accomplished by heating thetreated samples for predetermined time periods at temperatures selectedin the l40-l 65 C. range in a forced air draft oven. The samples werethen washed, dried to constant weight, etc., and subjected to thevarious evaluation tests traditionally employed for crosslinkingfinishes.

Typical experimental data on the properties of some cross linkedpolyoxymethylene coated cotton fabrics are described in the subsequentexamples with the aid of both tables and graphs. It need scarcely beemphasized that considering the very large number of possible reactionvariables which would all have to be explored to obtain a completeanalysis of their interactions and effects with respect to the productproperties these data illustrate trends only. It is understood that manypossible changes and modifications are possible and will become apparentto those skilled in the art from these detailed descriptions of exampleswithout departing from the scope of this invention.

Certain of the crosslinked oxymethylene polymer-coated cellulosicfabrics exhibit a substantially superior balance of performanceproperties compared to conventionally crosslinked cellulosic fabrics,particularly as regards strength retention, wrinkle recovery (wet anddry) and abrasion resistance qualities. This applies especially toselected methylol amidetype crosslinking agents includingdimethylolethyleneurea which is marketed commercially under the tradename Rhonite R-l. Rhonite R-l crosslinked oxymethylene-coated 80 X 80print cloth cotton fabrics show strength retention as high as 80 percentover a wide range of crosslinking agent add-ons together with goodwrinkle recovery values and satisfactory abrasion resistance. Forcomparison purposes conventionally Rhonite R-l crosslinked cellulosicfabrics are characterized by a substantial gain in wrinkle recoveryvalues-at the expense of strength losses of 50 percent or more as wellas much lower abrasion resistance. These properties can be viewed asdecreased apparel wearing qualities. Other widely used methylolamidecrosslinking agents show a similarly unsatisfactory behavior withcellulosic fabrics and definite improvements when they are applied tooxymethylcne polymer-coated fabrics.

The reasons for the improved balance of properties resulting from thecrosslinking of oxymethylene polymer-coated cellulosic fabrics are asyet not clearly understood. They are believed to be related to thephysical and chemical properties of the tough polyoxymethylene depositswhich surround the cellulose fibers. For conventionally crosslinkedcellulose fabrics, strength losses increase sharply at larger add-on'sof crosslinking agent. Above 12-15 percent add-on's strength retentionsare frequently as low as 40 percent. The treatment sequence embodied inthis invention is less sensitive to both polymer and crosslinking agentadd-on's. For Rhonite R-l crosslinked oxymethylene-coated fabrics,strength retentions remain in the order of percent for a wide range ofpolymer add-ons to which varying amounts of crosslinking agents havebeen applied.

It is noteworthy that. as expected, all the crosslinkedpolyoxymethylene-coated cotton fabrics proved to be insoluble uponimmersion in cuene. Experiments were also carried out to ascertain thethermal stability of these crosslinked polyoxymethylene-encapsulatedcotton cloths. Elevated temperature tests conducted in accordance withpreviously described procedures demonstrated a degree of thermalstability which is indicative of crosslinking with end capping.

EXAMPLE 5 Oxymethylene polymer-coated 80 X 80 desized, bleached andmercerized cotton print cloths prepared as described in Example 1 andcut into IO-inch X 6-inch fabric samples, were conditioned and thenpadded with an aqueous solution comprising 5 weight percent Rhonite R-ldimethylolethyleneurea, I weight percent of catalyst Zn(NO -6H O, 2weight percent Mykon SF polyethylene emulsion softener and 0.] weightpercent Triton X-405 wetting agent for approximately 10 minutes atambient temperatures. The padded textiles were then dried for 15 minutesat 80 C. in an air circulating oven. Curing or crosslinking was thencarried out at the much higher temperature of 165 C. for approximately2-5 minutes. The crosslinked polymer-coated cotton samples were thenwashed, dried to constant weight and subjected to the conventionalevaluation tests for crosslinked cellulosic fabrics. Typical results aresummarized in Table 3 and are shown graphically in FIG. 5 of theaccompanying drawing. The data are presented for crosslinking agentadd-ons in the order of 2-4 percent; this information is given foroxymethylene polymercoated fabrics containing up to 40 percent polymer.

The crosslinked oxymethylene polymer-coated cotton fabrics exhibitstrength retentions as high as 80 percent up to approximately 40 percentpolymer add-ons with only 2-4 weight percent Rhonite R-l crosslinkingagent. Good wrinkle recovery characteristics were obtained at relativelylow addon's together with satisfactory abrasion resistance. In contrast,the strength properties of conventional crosslinked uncoated cottonfabrics decrease sharply with greater polymer add-on's as shown clearlyin H6. 5.

EXAMPLE 6 Oxymethylene polymer-coated 80 X 80 desized, bleached andmercerized cotton print cloths prepared as described in Example I andcut into lO-inch X 6-inch fabric samples, were conditioned and thenpadded with an aqueous solution comprising 5 weight percent AerotexReactant LC unbufl'ered glyoxal-based reactant. 1 weight percent ofcatalyst Zn(N 0 h- 6H,O, 2 weight percent Mykon SF polyethylene emulsionsoftener and 0.1 weight percent Triton X-405 wetting agent forapproximately 10 minutes at ambient temperatures. The padded textileswere then dried for 15 minutes at 80 C. in an air circulating oven.Curing or crosslinking was then carried out at the much highertemperature of l60-165 C. for approximately 2-5 minutes. The crosslinkedpolymer-coated cotton samples were then washed, dried to constant weightand subjected to the conventional evaluation tests for crosslinkedcellulosic fabrics. Typical results are summarized in Table 4 and areshown graphically in FIG. 6 of the accompanying drawing. The data arepresented for crosslinking agent add-ons in the order of 2-4 percent;thus information is given for oxymethylene polymer-coated fabricscontaining up to 40 percent polymer.

The crosslinked oxymethylene-coated cotton fabrics exhibit strengthretentions in the order of 70 percent up to approx. 40 percent polymeradd-en's with only 2-4 percent weight Aerotex Reactant LC crosslinkingagent. Good wrinkle recovery characteristics were obtained at relativelylow addons together with satisfactory abrasion resistance. In contrastthe strength properties of conventionally crosslinked uncoated cottonfabric samples decrease sharply with greater crosslinking agent add-onsas is clearly also shown in FIG. 6.

EXAMPLE 7 This example explores the use of polyfunctional carboxylicacids for end capping the oxymethylene polymer coating and reaction withthe cotton cellulose. Oxymethylene polymercoated 80 X 80 desired,bleached and mercerized cotton print cloths prepared as described inExample 1 and cut into 10- inch X 6-inch fabric samples, wereconditioned and then padded successively with two aqueous solutions. Thefirst solution was comprised of weight percent sodium acetate and 0.1weight percent Triton X-lOO wetting agent while the second one contained2 weight percent of maleic acid. The cotton test samples were thendipped in the first solution for approximately 10 minutes in order topromote swelling of the cotton and facilitate the penetration of theesterification catalyst. After removal of excess solution, the sampleswere immersed in the solution of the maleic acid up to 10 minutes, driedat 80 C. for approximately 10 minutes and cured at selected temperaturesranging from 140l60 C. for l5-20 minutes in an air-circulating oven. Thesamples were then washed, dried to constant weight, etc., and subjectedto the customary fabric evaluation tests. Typical results are summarizedin Table 5. These data show that unsatisfactory results were obtainedwith this treatment.

EXAMPLE 8 This example describes the application of anotherpolycarboxylic acid for treatment with the oxymethylene polymercoatedcotton fabrics. Oxymethylene polymer-coated 80 X 80 desired, bleachedand mercerized cotton print cloths prepared as described in Example 1and cut into l0-inch 6-inch fabric samples, were conditioned then paddedsuccessively with two aqueous solutions. The first solution wascomprised of IS weight percent sodium acetate and 0.1 weight percentTriton X-l00 wetting agent, the second contained 2 weight percent of1,2,3,4 cyclopentane tetracarboxylic acid. The cotton test samples weredipped in the first solution for approximately 10 minutes in order topromote swelling of the cotton and facilitate the penetration of thecatalyst. After removal of ex cess solution, the samples were immersedin the solution of the acid for 10 minutes, dried at 80 C., then curedfor minutes at 150 C. in an air-circulating oven. The samples were thenwashed, dried to constant weight, etc., and subjected to the customaryfabric evaluation tests.

Typical results are summarized in Table 6. These data illustrate clearlyunsatisfactory results obtained with this treatment.

EXAMPLE 9 This example describes the treatment of oxymethylenepolymer-coated cotton fabrics with epichlorohydrin. Oxymethylenepolymer-coated 80 X 80 desized, bleached and mercerized cotton printcloths prepared as described in Example l and cut into IOinch X 6-inchfabric samples were conditioned then were reacted with epichlorohydrinin the presence of an alkaline catalyst using a two dip procedure.Reaction conditions were arranged in such a manner that thepolyoxymethylene polymer add-en's amounted to between 8 and l2 percent,based upon the initial weight of the conditioned cotton cloths. In thefirst process step, the samples were immersed in a 5 weight percentsodium hydroxide solution in absolute ethanol. Curing was accomplishedin an air circulating oven at C. for 10 minutes. The products were foundto be insoluble in cuene.

Data are summarized in Table 7. It will be noted that only very lowweight gains were obtained even though initial polyformaldehyde loadingof the cotton were quite substantial in certain cases. This indicatesthat the epichlorohydrin reaction degraded the polyoxymethylene underthe specific experimental conditions employed. This treatment istherefore not suitable for the proposed aims of this invention. Based onthe wrinkle recovery and strength retentions measured. the amount ofcrosslinking which had occurred. must have been limited. It isspecialized that the main reaction occurred between the polyformaldehydeand the epichlorohydrin.

TABLE 3 Some physical properties of polyoxymethylene-coated cottoncloths treated with Rhonite R-l crosslinking agent.

Breaking Strength Elonga- DWR" WW R" Sample Add-on (lb. tion' (W+F)(W+F) Control 43.5 21.5 195 185 CA"'l 1.5 24.0 22.0 272 C-A 2 3.2 19.821.9 296 279 C-A 3 3.6 18.7 19.9 317 C-A 4 1.5 29.0 24.1 284 268 C-A 52.1 23.0 19.3 302 231 3.7 38.3 23.2 288 270 232 6.8 39.3 23.5 271 259265 3.0 26.7 23.2 302 285 270 13.3 35.5 23.9 248 237 27 I 10.0 28.8 22.3272 9.6 28.8 20.0 225 16.0 35.8 19.0 235 18.7 37.2 17.7 196 236 18.333.8 18.2 200 175 237 22.1 38.5 19.3 238 25.4 48.0 22.9 153 140 227 27.048.0 23.0 310 26.2 32.8 16.4 297 33.6 36.2 17.2 151 138 320 36.8 38.815.8

""Percent add-on represents the total weight gain due to thepolyoxymethylene and the crmiulinking agent after cure except thosesamples designated C-A, etc. (See lnotnote e ""ASl M 01682-64, Averagenl'lhree mm. per sample, fill direction only.

" 'AS'IM D1 29560l; Average of three runs per simple.

'"ASI M Dl 2 15-60-1; Average of three runs per sample; samplesconditioned for five minutes in 0. I i Triton X-ltlU solution.

"'Contml samples treated with crosslinking agent only.

TABLE 4 Some physical properties of polyoxymethylene-coated cottoncloths treated with Aerotex React LC crosslinking agent.

Breaking Strength" Elonga- Dw Rm WW 8" Sample Add-on"' tlbs.) tion (W+F)(W+F Control 43.5 21.5 195 CB"l 2.9 27.2 23.2 298 C-B 2 1.7 30.7 24.9249 234 C-B 3 1.5 30.5 27.0 246 C-B 4 1.8 27.2 22.7 254 242 C-B 5 2.324.2 21.4 300 290 326 3.3 41.2 25.6 232 245 327 2.7 40.2 27.5 217 230328 3.7 43.7 27.1 205 313 6.5 31.5 20.0 325 6.8 32.3 22.4 244 8.7 30.019.1 303 9.5 44.3 27.7 187 329 12.5 32.5 19.8 323 15.9 27.3 18.3 195 178240 17.3 30.8 16.5

"" Percent add-on represents the total weight gain due to thepolyoxymethylene and the crosslinking agent after cure except thosesamples designated C-A. etc.

(See footnote e). ASTM Dl 682-64; Average of three runs per sample, filldirection only. ASTM D l295-60-T; Averageof three runs per sample.

'ASTM Dl29S-60-T', Average of three runs per sample; samples oonditionedl for five minutes in 0. I Triton X-IOO solution.

"" Control samples treated with croaslinlring agent only.

TABLE 5 Some physical properties of polyoxymethylene-coated cottoncloths treated with maleic acid.

Breaking l: Cure Strength DWR" Sample Add-on"" Ternperature (lb.) (W+F)Control 53 I66 Group A Group B 6l 9.3 160 3! 182 72 12.9 160 32 92 79[0.6 160 45 94 8 l l2.2 140 68 96 82 12.1 140 55 94 83 9.3 140 46 I 878.8 140 59 I00 Group C Percent add-on represents the total weight gaindue to the polyottymethylene and the croulinking agent alter curing.

"' All samples cured at the given temperature for minutes in aforced-dralt oven. ASTM-D l 682-64; Average of three runs per sample,warp direction only.

"' ASTM-D I 295-60-T; Average of five runs per sample.

TABLE 6 Some physical properties of poIyoxymethylene-coated cottoncloths treated with l,2,3,4-cyclopentane tetracarboxylic acid Breaking7v Strength Elon a- DWR" Sample Add-on (Ib.) tion" (W+F) Control 53 5.8175 Grou A I I0 7.5 I99 Group B I I l 5.5 36 5.4

n4 6 o as s 1 12s 4 l as s s w) s 9 4] s a Grou C 5 mi 3.3 39 5.6 no :u32 5.1 m 2.4 as 5.1 :28 2.6 32 5.x :29 3.6 230 :33 L9 229 M6 2.5 221 :413.2 so 5.: 14s as as 5.9

[5 Percent add-on represents the total weight gain due to thepolyolymethylene and the crosrlinking agent liter curing. ASTM-D l682-64; Average of three runs per sample, warp direction only. ASTM-D l2950-60-1; Average of five runs per sample. All samples dipped in 2%acid bath for It) minutes. dried at 80' C., then cured for 20 minutes atI50 C.

Elmendurf tear Percent Eklngit' Breaking Percent strength DWR WWR Sampleaddon (Ibs.l lion" Control 53 I3I. I32. I34. II7. I55. I56. I57. L58.I59.

I64. I65. I66. I67. I68. I69. I70. I7I. I72. I73. I74. I75. I76. I77.I78. I79. I80. IHI. I83. I84. I85. I36. I87..

I claim: 6 l. A process for imparting superior physical properties to acellulosic textile fabric, comprising:

a. wetting the surface of the cellulosic textile fabric with an alkalinecatalyst solution at ambient temperature;

b. applying highly purified anhydrous formaldehyde vapor to the surfaceof the catalyst-impregnated fabric to produce a fabric with a weightadd-on of about from 2 to 50 percent of a uniform and essentiallycontinuous oxymethylene polymer surface deposition; and

c. reacting the residual hydroxyl end groups of the oxymethylene polymerof the said surface deposition with a compound selected from the groupconsisting of acid anhydrides, epoxides, chloroalkylethers, andisocyanates, to retard high temperature depolymerization of saidcontinuous oxymethylene polymer.

2. A process for producing a crosslinked cellulosic textile fabrichaving superior physical properties, comprising:

a. wetting the surface of the cellulosic textile fabric with an alkalinecatalyst solution at ambient temperature;

b. applying highly purified anhydrous formaldehyde vapor to the surfaceof the catalyst-impregnated fabric to produce a fabric with a weightadd-on of about from 2 to 50 percent of a uniform and essentiallycontinuous or.- ymethylene polymer surface deposition;

c. reacting the residual hydroxyl end groups of the oxymethylene polymerof the said surface deposition with a compound selected from the groupconsisting of acid anhydrides, epoxides, chloroalkylethers, andisocyanates to retard highdternperature depolymerization of saidcontinuous oxymethylene polymer;

d. reacting the oxymethylene polymer-coated fabric of step (c) with asuitably catalyzed solution containing a crosslinking agent selectedfrom the group consisting of methylol derivatives of cyclic ureas,methylol derivatives of melamine, methylol derivatives of urea, andmethylol carbamates; and

e. then washing and drying the resulting oxymethylene polymer-coated andcrosslinked fabric to obtain shapeholding properties in the finishedfabric.

3. The cellulosic textile product produced by the process of claim 1.

4. The cellulosic textile product produced by the process of claim 2.

i i i I i

2. A process for producing a crosslinked cellulosic textile fabric having superior physical properties, comprising: a. wetting the surface of the cellulosic textile fabric with an alkaline catalyst solution at ambient temperature; b. applying highly purified anhydrous formaldehyde vapor to the surface of the catalyst-impregnated fabric to produce a fabric with a weight add-on of about from 2 to 50 percent of a uniform and essentially continuous oxymethylene polymer surface deposition; c. reacting the residual hydroxyl end groups of the oxymethylene polymer of the said surface deposition with a compound selected from the group consisting of acid anhydrides, epoxides, chloroalkylethers, and isocyanates to retard high-temperature depolymerization of said continuous oxymethylene polymer; d. reacting the oxymethylene polymer-coated fabric of step (c) with a suitably catalyzed solution containing a crosslinking agent selected from the group consisting of methylol derivatives of cyclic ureas, methylol derivatives of melamine, methylol derivatives of urea, and methylol carbamates; and e. then washing and drying the resulting oxymethylene polymer-coated and crosslinked fabric to obtain shape-holding properties in the finished fabric.
 3. The cellulosic textile product produced by the process of claim
 1. 4. The cellulosic textile product produced by the process of claim
 2. 